Purification of synthetic methanol



' June 8, 1937.

Was/zi@ ajenz l R. SCHEUBLE I PURIFICATION OF SYNTHETIC METHANOL Filed Sept. 11, 1934 l Agueoao crade methanol TH Was/zi@ agen? c plus mpurz'z'es *ff FXS j Aqueous purified fw; nef/zama! Rangs 'iii vHVVEJVTOR @Yue/olf i Scheable 35 thetically produced methanol is possible with action, the tower is illled with rings e which act .35

l 40 as are sarce1y miscible with Water and which similarly (as for example liquid sulphur dioxide), 40

,Y France .im 8,1931 'I y2li-,083,125

' UNITED sTATEs- PATENT oFi-icE I' 2,083,125

PURMCATIQN F SYNTHETIQ METHANOL -ltixdoli Schenble, vienna, Austria, asusitnor to I. G.

Farbenindnstrie Aktiengesellschaft, Frankforton-the-Main, Germany Application September 11, 1934, Serial No. 743,497

In Germany March 10, 1932 Claims.. (UL 2607-156) The present invention relates to the puriilcalaylei'; this may be recovered in known manner by tion of synthetic methanol, more particularly to fractional distillation. The second layer consistthe purification of crude methanol obtained from ing 0i the solvent and the impurities still .conthe oxides of carbon, especially carbon monoxider tains a certain amount of methanol. In order 5 and hydrogen by catalytic synthesis at higher torecover this,itispreferable after the rst treattemperatures and under high pressures. Metlinient to wash the solvent containing the imanol obtained in this` way always contains in purities with water which then absorbs the readdition to methanol other compounds, mainly mainder oi.' the methanol and a small amount oi those Containing Oxygen, especially higher althe impurities. This second washing water is cohols, in particular isobutyl alcohol and higher preferably used in` the purlilcation of further 10 homologues, aldehydes, such as isobutyraldehyde, amounts of crude methanol and thus returned to and ketones, for example, isobutyrone and cyclothe process. The separation oi' the solvent from pentanone. Theseparation oi these usually the impurities contained therein is eiie'cted in undesirable constituents from the methanol otlers the usual manner by fractional distillation. '15 considerable diiilculty, because the boiling point It is possible and, when working on a technical 15 of the undesirable substances extends over a scale preferable to carry out the Seid Pullfleawide range and many of these substances which tion in counter-current and continuously. are usually but slightly soluble in water form The nature of my invention will be. further constant boiling mixtures with water or with the described with reference to the accompanyuing o methanol itself. Separation by fractional disdrawing which illustrates -an arrangement of tillation is only possible with dliilculty, because apparatus suitable for carrying out the process the impurities occur in the rst runnings and according to this invention in counter-current, last runnings and also in the main fraction `conbut the invention is not restricted to the particu- SlSting chiefly 0f melhnnOl- I lar arrangement shown.'

The dilution of the crude synthetic methanol The apparatus consists of a washing tower into with a large amount of water for the purpose of which the washing agent, for example a benzine precipitating the water-insoluble constituents of fraction, is introduced towardsthe bottom of the the el'llde PIOdllCli Onli?` leads t0 unsatisfactory tower at a, while the aqueous methanol solution IeSultS- Experience has ShOWn that COIlSidcrable flows in at the top oi the tower at b. There are 3o amounts of the impurities always 'remain in the then formed in the washing. tower two layers, an 30 methanol S0` that numerous repetitions of the upper layer o! washing agent and a lower layer separation are necessary- This methed'oi puriof aqueous methanol, which are both continuction iS therefore uneconomical. ously withdrawn from the tower at c and d re- I have HOW found that the Dullflealln 0f Synspectively.v In order to increase the washing very satisfactory `results by treating the crude as distributingA bodies.

product or fractions 0f the same containing As suitable soiventsfmay be mentioned au methanol in the presence ef sufficientl amounts of organic liquids which are but slightly miscibie water with such organic or inorganic solvents with' water and inorganic liquids which behave have a' higher Solvent Power for the impurities provided these liquids have a higher solvent than for methanol' The amount of water nece" power for the substancesto be extracted than Sary in the Purmca'tion of the crude methanol m for methanol; that is to say the coefficient of accordance with the present process' varies with distribution of the methanol between the solvent the solubility of the solvent used 'in Water: The and water must be considerably less than'the 45 lower the s1ubmty ff the went in water' the coemcient or distribution of the impurities to be less water is afdded to themetha'nol' Generally. extracted. Solvents which have a lower boiling amounts of water of between about 1o to about oint than methanol and also those having a 30 cent b volume should be present in the p per by um d In this treatment two higher boiling point may be employed, but the methanol to e p e l former are preferable by reason of the fact that 0 layers are formed, namely an aqueous layer which containsthe methanol and a second layer con.. may be more conveniently separated from the gisting of the added solvent and the impurities methanol. Suitable organic solvents are, for

which were in the methanol. In some cases small example. light benzine. methylene chloride. chloramounts of the solvent remain in the aqueous benzene, higher ketenes. Snell 8S lebutylene. l55

esters. such as isoheptyl esters and carbon disulphide.

The process according to my invention allows of a convenient purification of `crude synthetic methanol and constitutes a great improvement over the known processes by reason of the sim-l plification of procedure and the saving oi steam in evaporation.

The following examples will further illustrate the nature `of my invention, but the invention is not restricted to these examples. The parts and percentages are by volume.

Example 1 Crude methanol obtained by catalytic synthesis from carbon monoxide and hydrogen is diluted with such an amount of water-that the mixture contains per cent of methanol. This mixture is extracted continuously in a countercurrent column, such-as is. shown in the accompanying drawing, with carbon disulphide, 15 parts of carbon disulphide being used for each parts of aqueous crude methanol. The methanol leaving the Ycolumn at d is subjected to a fractional distillation.' a first runnings containing carbon disulphide being rst obtained and `then pure methanol free from oily constituents.

The rst runnings is returned direct to the column. The carbon disulphide leaving the column at e is subjected to a fractional distillation in order to separate it from the impurities extracted from the crude methanol, and then returned to the column in circulation.

Ezample 2 lous methanol solution is washed with a benzine fraction boiling from 50 to 60 C. and consisting mainly of aliphatic hydrocarbons in counter-current in a washing tower such as that shown in the drawing.

The throughput of the two liquids through the tower is so adjusted that about equal parts pass through the tower and the bromine value of the eiliuent methanol falls to about 4. For example in this manner a methanol having a lbromine value of 560 can be washed to suchan extent that it has a bromine value of only 4.

The extracted methanol is subjected to a fractional distillation in a column. In this manner there are obtained a methanol rst runnings containing benzine, a main fraction being free from benzine and consisting mainly of pure methanol andhaving a bromine value of 1 and a less pure second runnings.

The rst runnings containing benzine is separated into benzine and methanol by dilution with water. The water containing methanol thus obtained may be added in the purificationof further amounts of crude methanol.

The amount of rst runnings containingbenl vthe fractional distillation Example 3 anol is reduced from 200 to 3.

It is also possible to carry out the washing continuously in a washing tower.

Example 4 100 kilograms of strongly contaminated synthetic methanol containing 30 per cent of water are washed with 100 kilograms of isobutyrone. By repeatedly washing the methanol layer in stages,v the bromine value may be reduced from 200 to 4. The purication may also be carried out continuously in a washing tower.

1. In the purication of synthetically produced methanol, the steps which comprise diluting crude methanol with water to an extent of between about 10 to about 35 per cent by volume and washing the resulting aqueous solution with a solvent which is scarcely miscible with water and with the aqueous methanol. which has a higher solvent power for the impurities than for methanol and which has a boiling point lower than' that of methanol.

2. In the purification of synthetically produced methanol, the steps which comprise diluting crude methanol with water to an extent of between aboutv 10 to about 35 per cent by volume and washing the resulting aqueous solution with a solvent which is scarcely miscible with Water and with the aqueous methanol and which has a higher solvent power for the impurities than for methanol.

3. In the purification of synthetically produced methanol, the steps which comprise diluting fractions of crude methanol to an extent of between about 10 to about 35 per cent by volume and washing the resulting aqueous solutions with a solvent which is scarcely miscible with water and with the aqueous methanol and which has a higher solvent power for the impurities than for methanoh 4. In the purification of synthetically produced methanol the steps which comprise diluting crude methanol with Water to an extent of between about 10 to about 35 per cent by volume and washing the resulting aqueous solution with a solvent which is scarcely miscible with water and with 'the aqueous methanol and which has a higher solvent power for the impurities than for methanol, separating the aqueous layer containing the methanol from the second layer comprising the added solvent and the impurities and subjecting the separated layers to fractional distillation.

5. The process as deiin inl claim 4, wherein the solvent layer is Washed with water prior to step.

RUDOLF SCHEUBLE. 

